Antenna arrays including waveguide antenna elements can provide desirable performance for communication over long distances. Passive antenna arrays with waveguide feed networks are one of the most suited technologies for antenna arrays because of the low level of losses they exhibit. As the number of antenna elements increases, the waveguide feed networks become increasingly complex and space consuming. This can be problematic in many environments (e.g., avionics) where space and/or weight are at a premium. In some cases, inter-element distance between the antenna elements may be constrained by the feed network size, which may degrade antenna performance.
A common problem with this type of architecture is grating lobes in the radiation pattern of the array, which happens if the inter-element distance is too large. Indeed, the fact that waveguides occupy more lateral space than other types of transmission medium (e.g., microstrip, etc.) can make it difficult to reduce the inter-element distance sufficiently to avoid grating lobes. This limitation can be even more severe with dual-polarized arrays, where the feed network system handles two channels, for the two orthogonal basis polarizations. Current architectures of dual-polarized antenna arrays using waveguide antenna elements use a larger than desired inter-element distance or sharing of a common excitation port among multiple antenna elements. These solutions can have drawbacks including increased grating lobes or reduced antenna efficiency.